Positron annihilation studies on pure and intercalated 2H-NbSe₂

Abstract

The layered transition metal dichalcogenide 2H-NbSe₂ and its intercalation compounds with ethylenediamine (EDA), Al and Cr metal atoms are investigated by positron angular correlation technique for the first time to gain information on their electronic structure. In 2H-NbSe₂ it is obvious that the angular distribution of annihilation photons can be fitted with two parabolae corresponding to the different electron densities which are characteristic of layer-like structure. On intercalation with EDA and metal atoms the Fermi momenta corresponding to two different directions come closer indicating a decrease in two dimensional character of the electron densities. The density of states at the Fermi level N(E_F) for pure 2H-NbSe₂ and its intercalated compounds has been estimated. The present results can be explained by charge transfer from the intercalate to the NbSe₂ layers.